What material is the Eiffel Tower primarily made of?

The Eiffel Tower is primarily made of wrought iron.

More precisely, its structure uses puddled iron, a refined form of wrought iron produced by processing molten pig iron. The material was manufactured in Lorraine, France, and assembled into a lattice of thousands of metal pieces. The tower’s open framework was designed to provide great strength without the solid bulk of masonry.

A common mix-up is to call the tower steel. Steel was becoming increasingly important in late-nineteenth-century construction, but the Eiffel Tower predates the widespread use of structural steel in major buildings. It is also not cast iron: cast iron is relatively brittle and is made by pouring molten iron into molds, whereas the tower’s wrought iron was worked into durable structural components.

The metal is protected from corrosion by regular painting. Gustave Eiffel recommended repainting the tower approximately every seven years, a maintenance tradition that helps preserve the landmark’s ironwork through changing weather conditions.